Category Archives: Fortnightly Weather Outlook

Subseasonal Weather Outlook (1 Apr – 15 Apr 2019)

Issued 31 Mar 2019
Valid for weeks 1 and 2: 1 Apr – 15 Apr

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

During this time of year, the Northeast Monsoon season typically weakens and transitions to the inter-monsoon period, during which more shower activities over the ASEAN region can be expected.

In the second week of April 2019, drier conditions are forecast to redevelop over many areas north of the Equator, except northern Viet Nam and parts of Lao PDR, Myanmar, and Cambodia. There are no other significant regional rainfall anomalies expected during the first fortnight.

Warmer temperatures are expected over Peninsular Malaysia and most parts of the Mekong sub-region except for Myanmar, particularly in the second week.

There is currently no significant signal shown by the Madden-Julian Oscillation (MJO), and most model predictions indicated no significant MJO activity would develop in the first half of April 2019.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (16 Mar – 31 Mar 2019)

Issued 15 Mar 2019
valid for weeks 3 and 4: 16 Mar – 31 Mar

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

In the coming fortnight, drier-than-average conditions are expected to continue over the Philippines and the equatorial region around the South China Sea.

Wetter-than-average conditions are expected to continue over the southern Maritime Continent during Week 3 but an easing of conditions are expected in in Week 4.

The Madden-Julian Oscillation (MJO) that has been active in Phase 4 since the second week of March 2019 is weakening and is expected to weaken further in the coming fortnight. This could bring wet weather to the southern parts of the Maritime Continent, in particular over the Java and Banda Sea areas in Week 3.

The prevailing dry and warm conditions over the Southeast Asia region can be attributed to the mass of dry air from a high pressure system in the Pacific Ocean that has extended over the Southeast Asia region. The dry mass of air is forecast to persist in Week 3, and is expected to bring warmer-than-average temperatures over most parts of the Mekong sub-region, Peninsular Malaysia and northern Sumatra.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (16 Jan – 31 Jan 2019)

Issued 26 Jan 2019
valid for weeks 3 and 4: 16 Jan – 31 Jan

 
Under the prevailing Northeast Monsoon condition, weather over the northern ASEAN region is expected to remain dry while scattered rain showers are expected over the southern ASEAN region.

No significant regional-scale rainfall anomaly is expected for most parts of the region, but coastal Viet Nam may experience wetter-than-normal weather in Week 3 due to a strengthening of northeasterly winds. Warmer temperatures experienced in many parts of western Southeast Asia region are expected to ease.

The MJO that has been active in the Pacific Ocean is expected to rapidly weaken by the start of the fortnight. However, it may re-emerge in the Indian Ocean or the western Maritime Continent during Week 4.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (1 Jan – 15 Jan 2019)

Issued 2 Jan 2019
valid for weeks 1 and 2: 1 Jan – 15 Jan

 
In the first week of the fortnight, a northeast monsoon surge is expected to bring wetter conditions over the South China Sea and over coastal Thailand and Viet Nam. Elsewhere in the Mekong sub-region, cooler conditions can be expected. The stronger monsoonal winds are likely to bring wetter weather to areas around the Java Sea as well. Conversely drier conditions are expected over the Philippines.

By week 2, the wetter conditions over the South China Sea are likely to spread southward to affect the north-eastern coast of Peninsular Malaysia and southern Thailand. Areas around the Java Sea are likely to become drier during the week.

The MJO is currently active in the western Pacific Ocean and is expected to continue propagating eastward. However, the strength and speed of the MJO are uncertain.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (16 Dec – 31 Dec 2018)

Issued 14 Dec 2018
valid for weeks 3 and 4: 16 Dec – 31 Dec

For the first week of the fortnight, wetter-than-average conditions are forecast over southern Thailand and along coastal Myanmar due to possible tropical cyclone formation over the Bay of Bengal.

Meanwhile, the Madden-Julian Oscillation (MJO) is forecast to propagate eastwards from Phase 3 to Phase 5 and possibly further in the coming fortnight. The MJO, together with a possible Northeast Monsoon surge, is expected to bring above-average rainfall over southern Viet Nam, Cambodia, southern Thailand and northern Peninsular Malaysia in the last week of December.

In the southern ASEAN region, drier-than-average conditions are likely over Java and its surrounding vicinity in the second half of the month.

Above-average temperatures are expected in parts of Thailand, northern Lao PDR, northern Viet Nam and western Cambodia for the second half of December. Elsewhere, temperatures are likely to be near-average.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (1 Dec – 15 Dec 2018)

Issued 3 Dec 2018
valid for weeks 1 and 2: 1 Dec – 15 Dec

 
The Northeast Monsoon season will bring the traditional dry season to the northern ASEAN region, and more shower activities to the southern ASEAN region.

Drier-than-usual conditions that have persisted over much of the Philippines and northern Borneo are forecast to continue.

There are signs of MJO strengthening in the Pacific Ocean. The MJO is expected to further develop and propagate through Phase 2 in the latter part of fortnight. This may bring more rainfall than average to the equatorial South China Sea region, with the highest likelihood over southern Thailand and northern Peninsular Malaysia towards the second week of December.

Temperatures in the Mekong sub-region are expected to be slightly warmer.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (16 Nov – 30 Nov 2018)

Issued 14 Nov 2018
valid for weeks 3 and 4: 16 Nov – 30 Nov

Climatologically, the northern ASEAN region experiences drier weather in the second half of November compared to the southern ASEAN region, where there would typically be more shower activities during this period. For the coming fortnight, drier-than-average conditions are expected over parts of Malaysia, Sumatra and Kalimantan. This is particularly so in the first week of the fortnight when the MJO is forecast to propagate eastwards through Phases 5 and 6. However, models’ predictions of the MJO development differ, with some models forecasting a weakening of the MJO during this period.

Slightly warmer temperatures are expected for the Mekong sub-region except for Myanmar. Near normal temperatures are predicted elsewhere.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

Subseasonal Weather Outlook (16 Oct – 31 Oct 2018)

Issued 15 Oct 2018
valid for weeks 3 and 4: 16 Oct – 31 Oct

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

From mid-October, wetter conditions may develop over Myanmar, especially over the coastal areas, due to an increase in rain showers that may be brought by tropical cyclones developing over the Bay of Bengal. The drier than normal conditions experienced by much of the Mekong sub-region in the first half of the month are likely to rescind, and a return to normal conditions can be expected for parts of the sub-region. Conditions are likely to be drier than normal in Viet Nam and the Philippines.

For the southern ASEAN region, drier conditions around the Java Sea area, including southern parts of Sumatra and Kalimantan, can be expected.

Warmer temperatures are forecast for the Mekong sub-region, and in Java and southern Sumatra.

The MJO signal is active in Phase 2 and may contribute to the development of tropical lows over the Bay of Bengal and the wet anomaly over coastal Myanmar. Most models predict the weakening of the MJO as it moves into the Maritime Continent.

The outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.